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RELIABILITY METHODS IN SHIP STRUCTURES

Emphasis is placed on the strength element in structural reliability, and the nominal strength of the hull girder and its different modes of failure are examined. A computer program has been developed for an approximate estimation of the longitudinal ultimate strength of single-deck ships, and its application to a large tanker is described. Factors that influence the as-built ultimate strength of a hull are discussed, and approximate formulations of the ultimate-strength coefficients of variation for the different failure modes as functions of the coefficients of their constitutive factors are also given. At present, it is important in any development work to consider several reliability models; this is made necessary by the lack of long-term records and experience. Three models are presnted; one of them, based on strength reduction and the load magnification factors, is discussed in some deail. Suggestion for further research on reliability methods in the analysis of ship structures are made for the three areas: loads, failure modes, and evaluation of past experience.